Dual crystal orientation for semiconductor devices

ABSTRACT

The present disclosure relates to a semiconductor device and a manufacturing method, and more particularly to a semiconductor device with fin structures having different top surface crystal orientations and/or different materials. The present disclosure provides a semiconductor structure including n-type FinFET devices and p-type FinFET devices with different top surface crystal orientations and with fin structures having different materials. The present disclosure provides a method to fabricate a semiconductor structure including n-type FinFET devices and p-type FinFET devices with different top surface crystal orientations and different materials to achieve optimized electron transport and hole transport. The present disclosure also provides a diode structure and a bipolar junction transistor structure that includes SiGe in the fin structures.

This application is a continuation of U S. Non-provisional Patentapplication Ser. No. 17/174,942, titled “Dual Crystal Orientation forSemiconductor Devices,” filed on Feb. 12, 2021, which is a continuationof U.S. Non-provisional patent application Ser. No. 16/426,660, titled“Dual Crystal Orientation for Semiconductor Devices,” filed on May 30,2019 (now U.S. Pat. No. 10,930,569), which claims the benefit of U.S.Provisional Patent Application No. 62/712,766, titled “Dual CrystalOrientation for Semiconductor Devices,” which was filed on Jul. 31,2018, all of which are incorporated herein by reference in theirentireties.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs, where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (e.g., the number of interconnecteddevices per chip area) has generally increased while geometry size(e.g., the smallest component or line that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the common practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features can be arbitrarily increased or reduced for clarity ofillustration and discussion,

FIG. 1 is a cross-sectional view of a partially-fabricated semiconductorstructure of FinFETs, in accordance with some embodiments.

FIG. 2 is an isometric view of a partially-fabricated semiconductorstructure of n-type FinFETs and p-type FinFETs, in accordance with someembodiments.

FIG. 3 is a flowchart of an exemplary method of forming apartially-fabricated semiconductor structure of n-type FinFETs andp-type FinFETs, in accordance with some embodiments.

FIGS. 4A-4M are a series of cross-sectional views ofpartially-fabricated semiconductor structures illustrating an exemplaryfabrication process of forming the partially-fabricated semiconductorstructure of n-type FinFETs and p-type FinFETs, in accordance with someembodiments.

FIG. 5 is a schematic of partially-fabricated semiconductor structures,in accordance with some embodiments.

FIG. 6 is a schematic of a partially-fabricated semiconductor structureof n-type FinFETs and p-type FinFETs, in accordance with someembodiments.

FIGS. 7A and 7B are schematics of an N+/p-type well diode and aP+/n-type well diode, respectively, in accordance with some embodiments.

FIGS. 8A and 8B are schematics of an NPV bipolar junction transistor anda PNP bipolar junction transistor, respectively, in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over a second feature in the description that followscan include embodiments in which the first and second features areformed in direct contact, and can also include embodiments in whichadditional features are disposed between the first and second features,such that the first and second features are not in direct contact. Inaddition, the present disclosure can repeat reference numerals and/orletters in the various examples. This repetition does not in itselfdictate a relationship between the various embodiments and/orconfigurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, can be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus can be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein can likewise be interpreted accordingly.

The acronym “FET,” as used herein, refers to a field-effect transistor.An example of a FET is a metal oxide semiconductor field-effecttransistor (MOSFET). MOSFETs can be, for example, (i) planar structuresbuilt in and on the planar surface of a substrate, such as asemiconductor wafer or (ii) built with vertical structures.

The term “FinFET” refers to a fin field-effect transistor, which is aFET that is formed over a fin and vertically oriented with respect tothe planar surface of a wafer.

“S/D” refers to the source and/or drain junctions that form twoterminals of a FET.

The term “vertical,” as used herein, means nominally perpendicular tothe surface of a substrate.

The expression “epitaxial layer” refers to a layer or structure ofsingle crystal material. Likewise, the expression “epitaxially grown”refers to a layer or structure of single crystal material.Epitaxially-grown material can be doped or undoped.

The term “nominal” as used herein refers to a desired, or target, valueof a characteristic or parameter for a component or a process operation,set during the design phase of a product or a process, together with arange of values above and/or below the desired value. The range ofvalues can be due to slight variations in manufacturing processes ortolerances.

The term “substantially” as used herein indicates the value of a givenquantity that can vary based on a particular technology node associatedwith the subject semiconductor device. Based on the particulartechnology node, the term “substantially” can indicate a value of agiven quantity that varies within, for example, =5% of a target (orintended) value.

The term “about” as used herein indicates the value of a given quantitythat can vary based on a particular technology node associated with thesubject semiconductor device. Based on the particular technology node,the term “about” can indicate a value of a given quantity that varieswithin, for example, 5-30% of the value (e.g., ±5%, ±10%, ±20%, or ±30%of the value).

Increasing performance of semiconductor devices on a substrate (e.g.,integrated circuit (IC) transistors, resistors, capacitors, diodes, etc.on a semiconductor (e.g., silicon) substrate) is critical andchallenging during design and manufacture of those devices. For example,during design and manufacture of, metal oxide semiconductor (MOS)transistor semiconductor devices, such as those used in a complementarymetal oxide semiconductor (CMOS), it is often desired to increaseperformance by increasing the movement of electrons (e.g., chargecarriers) in n-type MOS device (NMOS) channels and/or by increasing themovement of positive charged holes (e.g., charge carriers) in p-type MOSdevice (PMOS) channels. Increased charge carrier mobility can lead toincreased drive current (such as at drive current saturation), whichenhances device performance. One challenge is that electrons and holescan have different mobility values on the surface of semiconductorwafers (e.g., silicon wafer) having a particular crystal orientation.For example, electron transport is better on (100) wafer while holetransport is better on (110) surface. The different transportcharacteristics of electrons and holes can cause inferior and unbalancedperformance when fabricating both n-type FinFETs and p-type FinFETs onthe same substrate. To address this problem, this disclosure provides adevice structure with dual substrate orientation with n-type FinFETs andp-type FinFETs having different crystal orientations. In addition, thisdisclosure provides a device structure with silicon germanium (SiGe) inthe active layer to form a strained silicon device in order to increasemobility of charge carriers. In one aspect, this disclosure relates toFinFETs. A FinFET utilizes a vertical device structure. Channel regionsof the FinFET are formed in the fins, and gate structures are disposedover sidewalls and top surfaces of the fins. Gate structures surroundingthe channel provides the benefit of controlling the channel regions fromthree sides.

Various embodiments in accordance with this disclosure providesemiconductor device structures where the fin structures have differenttop surface crystal orientations and/or different materials to improveelectron and/or hole mobility to optimize device performance. In someembodiments, the disclosure provides a semiconductor structure includingn-type FinFET devices and p-type FinFET devices with different topsurface crystal orientations of the fin structures. In some embodiments,the disclosure provides n-type FinFET devices including a first finstructure having a first top surface crystal orientation (110) andp-type FinFET devices including a second fin structure having a secondtop surface crystal orientation (100). In some embodiments, thedisclosure provides n-type FinFET devices including a first finstructure having a first top surface crystal orientation (100) rotated45-degree and p-type FinFET devices including a second fin structurehaving a second top surface crystal orientation (100). In someembodiments, the disclosure provides a semiconductor structure includingn-type FinFET devices and p-type FinFET devices with different materialsof the fin structures. In some embodiments, the disclosure providesn-type FinFET devices including a first fin structure having a firstmaterial, such as silicon, and p-type FinFET devices including a secondfin structure having a second material, such as SiGe. In someembodiments, the disclosure provides a diode structure including SiGe inthe fin structure in some embodiments, the disclosure provides a bipolarjunction transistor structure including SiGe in the fin structure.

In accordance with various embodiments of this disclosure, using asemiconductor device structure with different crystal orientationsand/or different materials for fin structures for p-type FinFET devicesand n-type FinFET devices provides, among other things, benefits of (i)enhanced electron mobility; (ii) enhanced hole mobility, (iii) improveddrive current; (iv) optimized device performance; and (v) providing astreamlined, simple, and cost effective process to fabricate n-typeFinFET devices, p-type FinFET devices, and suitable other semiconductordevices such as bipolar junction transistor structures and diodes on thesame substrate with optimized drive current for the FinFET devices.

Before describing the embodiments of the present disclosure, anexemplary structure for a FinFET is presented. FIG. 1 provides anisometric view of a semiconductor device that includespartially-fabricated FinFETs, in accordance with some embodiments.

FIG. 1 is an isometric view of a semiconductor structure 100, inaccordance with some embodiment of the present disclosure. Semiconductorstructure 100 includes FinFET s. Specifically, semiconductor structure100 includes a substrate 102, a plurality of fins 104, a plurality ofisolation structures 106, and a gate structure 108. Gate structure 108is disposed over sidewalls and a top surface of each of fins 104. Fins104 and isolation structures 106 have top surfaces 114 and 118,respectively. Gate structure 108 includes a gate dielectric layer 115and a gate electrode structure 117. In some embodiments, one or moreadditional layers or structures can be included in gate structure 108.

FIG. 1 shows a hard mask 120 disposed on a top surface of gate electrodestructure 117. Hard mask 120 is used to pattern, such as by etching,gate structure 108. In some embodiments, hard mask 120 includes adielectric material, such as silicon nitride. The isometric view of FIG.1 is taken after the patterning process (e.g., etching) of a gatedielectric layer and a gate electrode layer to form gate structure 108.Integrated circuits can include a plurality of such, and similar, gatestructures.

Each of the plurality of fins 104 includes a pair of source/drain (S/D)terminals, where a source terminal is referred to as source region 110_(S) and a drain terminal is referred to as drain region 110 _(D). Thesource and drain regions 110 _(S) and 110 _(D) are interchangeable andare formed in, on, and/or surrounding fins 104. A channel region of fins104 underlies gate structure 108. Gate structure 108 has a gate length Land a gate width (2xH_(F)+W_(F)), as shown in FIG. 1 . In someembodiments, the gate length L is in a range from about 10 nm to about30 nm. In some embodiments, the gate length L is in a range from about 3nm to about 10 nm. In some embodiments, the fin width W_(F) is in arange from about 6 nm to about 12 nm. In some embodiments, the fin widthW_(F) is in a range from about 4 nm to about 6 nm. Gate height H_(G) ofgate structure 108, measured from a fin top surface 114 to the top ofgate structure 108, is in a range from about 50 nm to about 80 nm, insome embodiments. Fin height H_(F) of fin 104, measured from theisolation structure top surface 118 to fin top surface 114, is in arange from about 5 nm to about 100 nm, in some embodiments.

Substrate 102 can be a silicon substrate, according to some embodiments.In some embodiments, substrate 102 can be (i) another semiconductor,such as germanium; (ii) a compound semiconductor including siliconcarbide, gallium arsenide, gallium phosphide, indium phosphide, indiumarsenide, gallium arsenide phosphide (GaAsP), aluminum indium arsenide(AlInAs), aluminum gallium arsenide (AlGaAs), gallium indium arsenide(GaInAs), gallium indium phosphide (GalnP), gallium indium arsenidephosphide (GalnAsP), and/or indium antimonide; (iii) an alloysemiconductor including SiGe; or (iv) combinations thereof. In someembodiments, substrate 102 can be a silicon on insulator (SOI). In someembodiments, substrate 102 can be an epitaxial material.

Fins 104 are active regions where one or more transistors are formed.Fins 104 can include: (i) silicon (Si) or another elementarysemiconductor, such as germanium; (ii) a compound semiconductorincluding silicon carbide, gallium arsenide, gallium phosphide, indiumphosphide, indium arsenide, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP,GaInAsP and/or indium antimonide; (iii) an alloy semiconductor includingSiGe; or (iv) combinations thereof. Fins 104 can be fabricated usingsuitable processes, including patterning and etch processes. Thepatterning process can include forming a photoresist layer overlying thesubstrate (e.g., on a silicon layer), exposing the resist to a pattern,performing post-exposure bake processes, and developing the resist toform a masking element including the resist. The masking element canthen be used to protect regions of the substrate while an etch processforms recesses into substrate 102, leaving protruding fins. The recessescan be etched using a reactive ion etch (RIE) and/or other suitableprocesses. Numerous other methods to form fins 104 on substrate 102 canbe suitable. For example, fins 104 can include epitaxial material, inaccordance with some embodiments.

Isolation structures 106 can partially fill the recesses and can includea dielectric material such as, for example, silicon oxide,spin-on-glass, silicon nitride, silicon oxynitride, fluorine-dopedsilicate glass (FSG), a low-k dielectric material, other suitableinsulating material, and/or combinations thereof. In some embodiments,isolation structures 106 can be shallow trench isolation (STI)structures and can be formed by etching trenches in substrate 102. Thetrenches can be filled with insulating material, followed by achemical-mechanical polishing (CMP) and etch-back process. Otherfabrication techniques for isolation structures 106 and/or fins 104 arepossible. Isolation structures 106 can include a multi-layer structuresuch as, for example, a structure with one or more liner layers.Isolation structures 106 can also be formed by depositing an enhancedgap fill layer using the multi-step deposition and treatment process toeliminate voids and seams in the gap fill material.

Gate structure 108 can include a gate dielectric layer 115, a gateelectrode structure 117, and/or one or more additional layers, accordingto some embodiments. In some embodiments, gate structure 108 usespolysilicon as gate electrode structure 117. Also shown in FIG. 1 is ahard mask 120 disposed on a top surface of gate electrode structure 117.Hard mask 120 is used to pattern, such as by etching, gate structure108. In some embodiments, hard mask 120 includes a dielectric material,such as silicon nitride.

Although gate structure 108 is described as using polysilicon oramorphous silicon for gate electrode structure 117, gate structure 108can be a sacrificial gate structure, such as a gate structure formed ina replacement gate process for a metal gate structure. The replacementgate process and associated manufacturing steps can be performed and arenot shown in these figures. The metal gate structure can include barrierlayer(s), gate dielectric layer(s), work function layer(s), fill metallayer(s), and/or other suitable materials for a metal gate structure. Insome embodiments, the metal gate structure can include capping layers,etch stop layers, and/or other suitable materials.

Exemplary p-type work function metals that can be included in the metalgate structure are TiN, tantalum nitride (TaN), ruthenium (Ru),molybdenum (Mo), aluminum (Al), tungsten nitride (WN), zirconiumdisilicide (ZrSi₂), molybdenum disilicide (MoSia), tantalum disilicide(TaSi₂), nickel disilicide (NiSiz), platinum (Pt), other suitable p-typework function materials, or combinations thereof. Exemplary n-type workfunction metals that can be included in the metal gate structure are Al,titanium (Ti), silver (Ag), tantalum aluminum (TaAI), tantalum aluminumcarbon (TaAlC), tantalum aluminum nitride (TiAIN), tantalum carbide(Tac), tantalum carbide nitride (TaCN), tantalum silicide nitride(TaSiN), manganese (Mn), zirconium (Zr), other suitable n-type workfunction materials, or combinations thereof. A work function isassociated with the material composition of the work function layer.Thus, the material of a work function layer can be chosen to tune itswork function so that a desired threshold voltage W is achieved by adevice formed in the respective region. The work function layer(s) canbe deposited by chemical vapor deposition (CVD), plasma-enhanced CVD(PECVD), atomic layer deposition (ALD), other suitable processes, and/orcombinations thereof.

A fill metal layer can be deposited over the work function metallayer(s). The fill metal layer fills in remaining portions of trenchesor openings formed by removal of the sacrificial gate structure. Thefill metal layer can include Al, W, copper (Cu), and/or other suitablematerials. The fill metal can be formed by ALD, CVD, physical vapordeposition (PVD), plating, other suitable processes, and/or combinationsthereof.

Semiconductor device structure 100 described above includes fins 104 andgate structure 108. The semiconductor device structure 100 can includemultiple gate structures 108 formed over fins 104. The semiconductordevice structure 100 can include additional processing to form variousfeatures such as, for example, lightly-doped-drain (LDD) regions anddoped S/D structures. The term “LDD region” is used to describelightly-doped regions disposed between a channel region of a transistorand at least one of the transistor's S/D regions. LDD regions can beformed in fins 104 by doping. Ion implantation can be used, for example,for the doping process. Other processes can be used for doping the LDDregions.

FIGS. 2, 3, 5, 6, 7A-7B, and 8A-8B illustrate various semiconductordevices according to different embodiments in this disclosure. FIG. 3 isa flow chart of an example fabrication process of a semiconductor devicethat includes both n-type FinFET and p-type FinFET. FIGS. 4A-4Millustrate an example fabrication process of a semiconductor device thatincludes both n-type FinFET and p-type FinFET, showing cross sectionalviews of the semiconductor device structure during various stages offabrication. The fabrication process provided herein is exemplary, andadditional operations can be performed. These additional operations arenot shown in the figures for simplicity.

FIG. 2 is a 3D view of an exemplary partially-fabricated semiconductorstructure 200 including partially-fabricated n-type FinFET devices 250and partially-fabricated p-type FinFET devices 260, after a plurality offirst fin structures 210 and second fin structures 220 formed onsubstrate 202, in accordance with some embodiments.

Substrate 202 can include silicon or some other suitable elementarysemiconductor such as, for example, diamond or germanium (Ge); asuitable compound semiconductor such as, for example, silicon carbide(SiC), indium arsenide (InAs), or indium phosphide (InP); or a suitablealloy semiconductor such as, for example, silicon germanium carbide(SiGeC), gallium arsenic phosphide (GaAsP), gallium indium phosphide(GalnP), or silicon on insulator (SOI). In some embodiments, substrate202 can be a silicon wafer. In some embodiments, substrate 202 can be asilicon on insulator (SOI) wafer.

Silicon wafers can be grown from crystal having a regular crystalstructure, with silicon having a diamond cubic structure with an examplelattice spacing of about 5.4 Å (about 0.54 nm). In one process forforming the silicon wafer, a cylindrical ingot of high purity monocrystalline silicon, is sliced with a wafer saw and polished to formwafers. During the slicing process, the surface is aligned in one ofseveral relative directions known as crystal orientations. Orientationis defined by the Miller index with (100) or (111) faces being exampleorientations for silicon. Orientation is important since many of asingle crystal's structural and electronic properties are highlyanisotropic. For example, electron mobility is higher on the (100) planethan on the (110) plane since each direction offers distinct paths forcharge transport. Ion implantation depths also depend on the wafer'scrystal orientation, since each direction offers distinct paths for iontransport. In some embodiments, substrate 202 can include silicon havinga (100) top surface crystal orientation.

In some embodiments, first tin structures 210 and second fin structures220 protrude from substrate 202, as illustrated by FIG. 2 . In someembodiments, first fin structures 210 and second fin structures 220 areparallel and extend in one direction (e.g., z-direction). Although fourfin structures are illustrated in FIG. 2 , fewer or more fin structurescan be included in semiconductor structure 200. First fin structures 210and second fin structures 220 can include silicon or some other suitableelementary semiconductor materials such as, for example, diamond orgermanium (Ge); a suitable compound semiconductor such as, for example,silicon carbide (SiC), indium arsenide (InAs), or indium phosphide(InP); or a suitable alloy semiconductor such as, for example, silicongermanium carbide (SiGeC), gallium arsenic phosphide (GaAsP), or galliumindium phosphide (GalnP). In some embodiments, first fin structures 210can include a first material including, but not limited to, silicon. Insome embodiments, second fin structures 220 can include a secondmaterial including, but not limited to, SiGe. In some embodiments, firstfin structures 210 can be doped with n-type dopants such as, forexample, phosphorus (P) and arsenide (As). In some embodiments, secondfin structures 220 can be doped with p-type dopants such as, forexample, boron (B) and gallium (Ga). In some embodiments, the first finstructures can be doped with n-type dopants and serve as n-type FinFETs(e.g., NMOS devices), while the second fin structures can be doped withp-type dopants and serve p-type FinFETs (e.g., PMOS devices).

In some embodiments, first fin structures 210 can include silicon having(110) or (100) rotated 45-degree ((100) R45) crystal orientation. Insome embodiments, second fin structures 220 can include SiGe having(100) crystal orientation. The fin structures can include a top surfaceand sidewalls having different crystal orientations. For example, when asilicon substrate is grown to have a fin top surface (210) crystalorientation (110) or (100) rotated 45-degree ((100) R45), an indexsystem for a crystal plane in an active layout for forming the fin isset such that the sidewalls (210 _(sw)) of the first fin structures havea (100) sidewalls crystal orientation And in this case, first finstructures 210 is referred to as having (110) top surface crystalorientation or (100) rotated 45-degree ((100) R45) top surface crystalorientation. Similarly, when a silicon substrate is grown to have a fintop surface (220 _(t)) crystal orientation (100), an index system for acrystal plane in an active layout for forming the second fin structureis set such that the sidewalls of the second fin structures have a (110)sidewalls crystal orientation. And in this case, the second finstructure is referred to as having (100) top surface crystalorientation. In some embodiments, the sidewalls of the fin structurescarry a significant portion of the S/D current (as compared to the topsurfaces of the fin structures), and electron mobility is higher on the(100) plane and the hole mobility is higher on the (110) plane.Therefore, by selectively choosing the dual crystal orientation for thefirst and the second fin structures, electron transport of the first finstructures (e.g., n-type FinFET) and hole transport of the second finstructures (e.g., p-type FinFET) can be optimized.

In some embodiments, first fin structures 210 and second fin structures220 are formed by patterning a hard mask layer and etching intosubstrate 202 using an anisotropic etch (e.g., dry etch). In someembodiments, the anisotropic etch uses chlorine and/or fluorine-basedchemicals. The areas covered by hard mask layer are blocked by the hardmask layer during the anisotropic etch process, and the areas notcovered by hard mask layer are recessed, resulting in first finstructures 210 and second fin structures 220.

In some embodiments, semiconductor device 200 can include isolationstructures 206 formed over substrate 202 and on opposing sidewalls offirst fin structures 210 and second fin structures 220. In someembodiments, isolation structures 206 can fill the openings betweenfirst tin structures 210 and second fin structures 220 and provideisolation between the adjacent fins. Isolation structures 206 caninclude a dielectric material such as, for example, silicon oxide,spin-on-glass, silicon nitride, silicon oxynitride, FSG, a low-kdielectric material, other suitable insulating material, and/orcombinations thereof. In some embodiments, isolation structures 206 canbe shallow trench isolation (STI) structures and can be formed bydepositing insulating material to fill the openings and followed by aCMP and an etch-back process. Isolation structures 206 can include amulti-layer structure such as, for example, a structure with one or moreliner layers. Isolation structures 206 can also be formed by depositingan enhanced gap fill layer using the multi-step deposition and treatmentprocess to eliminate voids and seams in the gap till material. Isolationstructures 206 can be formed by an etch back process by removing thehard mask layer and etching back a portion of the deposited material toform isolation structures 206. In some embodiments, removing the hardmask layer includes performing a wet chemical process with phosphoricacid (H₃PO₄) that etches silicon nitride. In some embodiments, the hardmask layer can be removed using a CMP process.

After the hard mask layer is removed, isolation structures 206 can beetched back to expose a portion of first fin structures 210 and secondfin structures 220. In some embodiments, isolation structures 206 areetched back so that the top surface of the remaining isolationstructures is below the top surface of the first fin structures 210 andsecond fin structures 220. The etch processes in isolation structures206 can be plasma processes, for example, a reactive ion etching (RIE)process using oxygen-based plasma. In some embodiments, the RIE etchingprocess can include other etchant gas such as, for example, nitrogen,carbon tetrafluoride (CF₄), and/or other suitable gases. Numerous othermethods to etch back the isolation structure can be suitable. In someembodiments, the height of the first fin structures 210 and second finstructures 220 measured from the top surface of the remaining isolationstructures 206 to the top surface of first fin structures 210 and secondfin structures 220 is between about 50 nm and about 90 nm (e.g., between65 nm and 70 nm). After isolation structures 206 are etched back,portions of first fin structures 210 and second fin structures 220 canprotrude from the remaining portions of isolation structures 206. Insome embodiments, a gate structure (not shown) can be formed over thefirst and second fin structures. In some embodiments, semiconductorstructure 200 can include one or more n-type FinFET devices and one ormore p-type FinFET devices.

FIG. 3 is a flowchart of an exemplary method 300 of forming asemiconductor device, according to some embodiments of the presentdisclosure. Operations can be performed in a different order or notperformed depending on specific applications. Method 300 is describedwith reference to fabrication processes and structures illustrated inFIGS. 4A-4M. It should be noted that method 300 does not produce acomplete semiconductor structure 100 as shown in FIG. 1 . Accordingly,it is understood that additional processes can be provided before,during, and after method 300.

Referring to FIG. 3 , method 300 starts at operation 302, in which asubstrate is provided. As illustrated in FIG. 4A, substrate 401 can be asilicon-on-insulator wafer having a device layer 410 _(A) separated froma Si substrate 402 by a buried oxide (BOX) layer 408 _(A). In someembodiments, buried oxide layer can have a thickness between about 5 nmand about 15 nm.

In some embodiments, Si substrate 402 can have top surface crystalorientation (100). In some embodiments, device layer 410 _(A) can havetop surface crystal orientation (110) or (100) R45. Substrate 401 can beformed by various wafer bonding techniques. During the wafer bondingprocess, a donor wafer (e.g., device layer 410 _(A)) can be bonded to ahandle wafer (e.g. Si substrate 402) each having a different top surfacecrystal orientation. Prior to bonding, both wafers can be prepared witha pretreatment process including cleaning, plasma surface activation,growth of bonding layer or a combination thereof, to facilitate highstrength-void free bonding. In some embodiments, the plasma surfaceactivation can be achieved by hydrophobic, hydrophilic, direct surfacestates, or other processes. In some embodiments, the substrates can becleaned with HF prior to bonding. Following the bonding, a hightemperature anneal can be used to strengthen the bond interface (e.g.,between 410 _(A) and 402). In some embodiments, the high temperatureanneal can be carried out at temperatures ranging from 300° C. to 1100°C. In some embodiments, the bonded substrates can be annealed at about600° C. In some embodiments, oxide layers (e.g., buried oxide (BOX)layer 408 _(A)) can be formed on one or both surfaces of the donor waferand handle wafer. Examples of materials, which can be used for oxidelayers, include but are not limited to, silicon dioxide (SiO₂), siliconnitride (Si₃N₄), plasma oxide and chemical oxide, or high-dielectricconstant based oxides, such as hafnium oxide. Oxide layer formation canbe performed by a variety of processes, including, but not limited to,ambient native growth, chemical growth, chemical vapor deposition (CVD),RF sputtering, atomic layer deposition (ALD), low pressure CVD,plasma-enhanced CVD or any other suitable process.

Subsequently, as shown in FIG. 4B, a bi-layer hard mask including oxidehard mask 436 _(B) and nitride hard mask 438 _(B) can be disposed ondevice layer 410 _(A). In some embodiments, the thickness of the oxidehard mask 436 _(B) is between about 40 nm and about 80 nm (e.g., between40 nm and 80 nm), and the thickness of the nitride hard mask 438 _(B) isbetween about 10 nm and about 30 nm (e.g., between 10 nm and 30 nm). Insome embodiments, oxide hard mask 436 _(B) includes SiO_(x), and nitridehard mask 438 _(B) includes silicon nitride (SiN_(x)) or silicon carbonnitride (SiCN). In some embodiments, the oxide hard mask 436 _(B) can bea thin film including silicon oxide formed, for example, using a thermaloxidation process. In some embodiments, nitride hard mask 438 _(B) caninclude silicon nitride formed by, for example, low pressure chemicalvapor deposition (LPCVD) or plasma enhanced CVD (PECVD).

Referring to FIG. 3 , method 300 proceeds to operation 304, in which aportion of device layer is removed. As illustrated in FIG. 4C, a portionof device layer 410 _(A) (as shown in FIG. 4B) is removed to formopenings at selected locations. And patterned device layer 410 _(C) candefine a region for further n-type finFET device fabrication. Openingscan be formed at selected locations by removing oxide hard mask 436 _(B)and nitride hard mask 438 _(B) and etching back a portion of devicelayer 410 _(A). In some embodiments, the etching stops on buried oxide(BOX) layer 408 _(A). In some embodiments, the removal of oxide hardmask 436 _(B) and nitride hard mask 438 _(B) can be performed using adry etching process (e.g., reaction ion etching) or a wet etchingprocess. In some embodiments, the removal of nitride hard mask 438S caninclude performing a wet chemical process with H₃PO₄ that etches siliconnitride. In some embodiments, an exemplary fabrication process caninclude forming photoresist layer 440 overlying the semiconductorstructure, exposing the photoresist to a mask having a pattern thereon,performing a post-exposure bake process, and developing the resist toform a masking layer over oxide hard mask 436 _(C).

Referring to FIG. 3 , method 300 proceeds to operation 306, in which aspacer is disposed over the device layer. As illustrated in FIG. 4D,spacer 436 _(D) is formed on top and side surfaces of device layer 410_(C). Spacer 436 _(D) can be a low-k spacer with a dielectric constantless than 3.9. In some embodiments, spacer 436 _(D) can includeelements, such as silicon (Si), oxygen (O), carbon (C) or combinationsthereof. In some embodiments, the thickness of spacer 436 _(D) isbetween about 6 nm and about 8 nm. In some embodiments, forming spacer436 _(D) includes a blanket deposition of a spacer layer followed bypulling back the spacer layer with an etch (e.g. a dry etch) process. Insome embodiments, pulling back the spacer layer includes etching andremoving the spacer layer and a portion of buried oxide layer 408 _(A)to expose a portion of Si substrate 402.

Referring to FIG. 3 , method 300 proceeds to operation 308, in which aSiGe epitaxy layer is formed. As illustrated in FIG. 4E, SiGe epitaxylayer (420 _(E)) is formed over a portion of substrate 402, where thedevice layer on the portion of substrate 402 is removed. In someembodiments, the SiGe epitaxy layer is formed at a temperature betweenabout 400° C. and about 500° C. The epitaxy layer forming process can bea selective process that grows the epitaxy layer on the exposed surfacesof the silicon substrate. The growth process continues until a nominalsize and/or structure of epitaxial SiGe has been reached.

Referring to FIG. 3 , method 300 proceeds to operation 310, in which thedevice layer and the SiGe epitaxy layer are planarized. As illustratedin FIG. 4F, a planarization process (e.g., a CMP process) is performedto planarize the top surfaces of the semiconductor structure to formplanarized device layer 410 _(F) and SiGe epitaxy layer 420 _(F). Insome embodiments, after SiGe epitaxy layer formation and prior to CMPplanarization, oxide hard mask and spacer can be removed by wet etch. Insome embodiments, a preliminary planarization of the structure can beperformed, including depositing a tri-layer of polysilicon, siliconnitride, and polysilicon 434 over the device layer and SiGe epitaxylayer, applying a CMP planarization process which stops on the middlesilicon nitride layer, and performing a dry etch process to further etchback the semiconductor structure until the epitaxial SiGe is exposed.

Referring to FIG. 3 , method 300 proceeds to operation 312, in which thedevice layer and SiGe epitaxy layer are etched to form a plurality offin structures. As illustrated in FIG. 4G and FIG. 4H, the formation offin structures can include (i) forming and patterning a hard mask layeron device layer 410 _(F) and SiGe epitaxy layer 420 _(F) to form apatterned hard mask layer 437, and (ii) etching device layer 410 _(F),SiGe epitaxy layer 420 _(F) and Si substrate 402 through patterned hardmask layer 437. Patterned hard mask layer 437 can include thin oxidelayer 413, nitrite hard mask 432 _(C) and oxide hard mask layer 117. Theetching can be performed using, for example, a dry etch process, a wetetch process, or a combination thereof. The dry etch process can usereactive ion etching using a chlorine or fluorine-based etchant. In someembodiments, the hard mask layer can be a thin film including siliconoxide formed, for example, using a thermal oxidation process. In someembodiments, hard mask layer can include silicon nitride formed by, forexample, low pressure chemical vapor deposition (LPCVD) or plasmaenhanced (ND (PECVD).

Referring to FIG. 3 , method 300 proceeds to operation 314, in which anSTI recess is formed between the fin structures. As illustrated in FIG.4I and FIG. 4J, the formation of STI recess 412 _(J) can include (i)depositing protective layer including Si liner 414 and SiN liner 416 onthe structure of FIG. 4H; (ii) depositing a layer of insulating materialin STI region 4121 on the protective layer; (iii) annealing the layer ofinsulating material; (iv) chemical mechanical polishing (CMP) theannealed layer of insulating material; and (v) etching the polishedstructure to form STI recess 412 _(J). The protective layer including Siliner 414 and SiN liner 416 can be deposited using, for example, ALD orCVD. The protective layer can help to prevent oxidation of finstructures during the annealing process of the layer of insulatingmaterial.

In some embodiments, the layer of insulating material can include, forexample, silicon oxide, silicon nitride, silicon oxynitride,fluoride-doped silicate glass (FSG), or a low-k dielectric material. Insome embodiments, deposition of the layer of insulating material can beperformed using any deposition methods suitable for flowable dielectricmaterials (e.g., flowable silicon oxide). For example, flowable siliconoxide can be deposited for STI region 412 _(I) using a flowable CVD(FCVD) process. The FCVD process can be followed by a wet annealprocess. The wet anneal process can include annealing the depositedlayer of insulating material in steam at a temperature in a range fromabout 200° C. to about 700° C. for a period in a range from about 30 minto about 120 min. The wet anneal process can be followed by the CMPprocess that can remove the patterned hard mask layer and portions ofthe layer of the insulating material to substantially co-planarize a topsurface of the layer of insulating material with top surfaces of finstructures. The CMFP process can be followed by the etching process toetch back the layer of insulating material, the protective layer, andremaining nitride hard mask on the fin structures to form the structureof FIG. 4J.

The etch back of the layer of insulating material can be performed, forexample, by a dry etch process, a wet etch process, or a combinationthereof. In some embodiments, the dry etch process can include using aplasma dry etch with a gas mixture having octafluorocyclobutane (C₄F₈),argon (Ar), oxygen (O₂), and helium (He), fluoroform (CHF₃) and He,carbon tetrafluoride (CF₄), difluoromethane (CH₂F₂), chlorine (C₂), andO₂, hydrogen bromide (HBr), O₂, and He, or a combination thereof with apressure ranging from about 1 mTorr to about 5 mTorr. In someembodiments, the wet etch process can include using a dilutedhydrofluoric acid (DHF) treatment, an ammonium peroxide mixture (APM), asulfuric peroxide mixture (SPM), hot deionized water (DI water), or acombination thereof. In some embodiments, the wet etch process caninclude the use ammonia (NH₃) and hydrofluoric acid (HF) as etchants andinert gases such as, for example, Ar, xenon (Xe), He, or a combinationthereof. In some embodiments, the flow rate of NHF and NHL used in thewet etch process can each range from about 10 sccm to about 100 sccm(e.g., about 20 sccm, 30 sccm, or 40 sccm). In some embodiments, the wetetch process can be performed at a pressure ranging from about 5 mTorrto about 100 mTorr (e.g., about 20 mTorr, about 30 mTorr, or about 40mTorr) and a high temperature ranging from about 50° C. to about 120° C.

Referring to FIG. 3 , method 300 proceeds to operation 316, in which oneor more recessed fin structure are formed. As illustrated in FIGS. 4Kand 4L, the formation of the one or more recessed fin structures caninclude (i) depositing dummy oxide layer 426 on the semiconductorstructure of FIG. 4J; (ii) depositing polysilicon 418 _(K) over dummyoxide layer 426; and (iii) reducing the height of the fin structures byan etching process (e.g., CMP). In some embodiments, after the etchingprocess, a first plurality of recessed fin structures can includeremaining Si 410 _(L) having (110) or (100) R45 orientation on topsurface. In some embodiments, after the etching process, a secondplurality of recessed fin structure 420 can include remaining SiGehaving (100) orientation on top surface. In some embodiments, dummyoxide layer can be formed by a variety of processes, including, but notlimited to, chemical growth, chemical vapor deposition (CVD), RFsputtering, atomic layer deposition (ALD), low pressure CVD,plasma-enhanced CVD or any other suitable process. In some embodiments,polysilicon can be formed by a variety of processes, including, but notlimited to, chemical vapor deposition (CVD), physical vapor deposition(PVD), atomic layer deposition (ALD), other suitable deposition methods,or a combination thereof.

Referring to FIG. 3 , method 300 proceeds to operation 318, in which ashallow recess source/drain epitaxy layer is formed on the remaining Si.As illustrated in FIG. 4M, shallow recess source/drain epitaxy structure410 is formed on the remaining Si 410 _(L) (not shown in FIG. 4M butshown in FIG. 4L). In some embodiments, shallow recess source/drainepitaxy structure 410 can be grown by an epitaxial deposition/partialetch process, which can be a cyclic deposition etch process that repeatsthe epitaxial deposition/partial etch process at least once. In someembodiments, shallow recess source/drain epitaxy structure 410 can begrown by selective epitaxial growth (SEG), where an etching gas is addedto promote the selective growth of semiconductor material on the exposedsurfaces of remaining Si 410 _(L) of the recessed fin structures, butnot on insulating material (e.g., dielectric material of STI recess).

In some embodiments, epitaxial source/drains 422 and 424 are formed onshallow recess source/drain epitaxy structure 410 and recessed finstructure 420, respectively. In some embodiments, shallow recesssource/drain epitaxy structure 410 can have a thickness between about 3nm and about 10 nm. In some embodiments, buried oxide layer 408 can havea thickness between about 5 nm and about 15 nm. In some embodiments,recessed fin structure 420 can have a thickness between about 5 nm andabout 15 nm. In some embodiments, recessed fin structure 420 can bedoped with p-type dopants to form a buried channel region. In someembodiments, the buried channel region can have a thickness betweenabout 5 nm and about 15 nm. In some embodiments, shallow recesssource/drain epitaxy structure 410 can be doped with n-type dopants toform a first channel region and recessed fin structure 420 can be dopedwith p-type dopants to form a second channel region. In someembodiments, the second channel region can be a buried channel region.In some embodiments, thickness of the first channel region can bebetween about 3 nm and about 10 nm. In some embodiments, thickness ofthe second channel region can be between about 5 nm and about 15 nm. Insome embodiments, thickness of the first channel region is less than thethickness of the second channel region.

In some embodiments, epitaxial source/drains 422 and 424 are formed bygrowing epitaxial layers over exposed surfaces of shallow recesssource/drain epitaxy structure 410 and recessed fin structure 420.Growing the epitaxy layers on exposed surfaces of shallow recesssource/drain epitaxy structure 410 and recessed fin structure 420 caninclude performing a pre-clean process to remove the native oxide on thesurface of shallow recess source/drain epitaxy structure 410 andrecessed fin structure 420. Next, an epitaxy process can be performed togrow the epitaxy layers on the surfaces of shallow recess source/drainepitaxy structure 410 and recessed fin structure 420. In someembodiments, as shown in FIGS. 4K-4M, fin structures 410 _(H) and 420_(H) are etched back using a suitable etching process such as, forexample, a dry RIE etching process. An epitaxy process can then beperformed to grow epitaxy layers from the top surfaces of shallow recesssource/drain epitaxy structure 410 and recessed fin structure 420. Theepitaxy process can use the top surfaces of shallow recess source/drainepitaxy structure 410 and recessed fin structure 420 as a seed layer andthe growth process continues until a nominal size and/or structure ofepitaxial source/drains 422 and 424 has been reached. An in-situ dopingprocess can also be performed during the epitaxy process. In someembodiments, the epitaxy process is an SiGe epitaxy process performed ata temperature between about 400° C. and about 500° C. (e.g., between400° C. and 500° C.). The epitaxy process can be a selective processthat grows the epitaxy layer on the exposed surfaces of the finstructures. The growth process can continue until a nominal size and/orstructure of epitaxial source/drains 422 and 424 has been reached. Insome embodiments, epitaxial source/drains 422 can include Si. In someembodiments, epitaxial source/drains 424 can include SiGe. In someembodiments, the thickness of epitaxial source/drains 422 and 424 isbetween about 10 nm and about 20 nm. In some embodiments, epitaxialsource/drains 422 and 424 are doped with p-type or n-type dopants duringthe epitaxy process. For example, epitaxial source/drains 422 can bedoped with phosphor (IP), and epitaxial source/drains 424 can be dopedwith boron (B) during the epitaxy process.

The epitaxial source/drains 422 and 424 can also take different shapesdepending on various factors such as, for example, the epitaxy processcondition, the crystalline orientation of fin structures, and/or othersuitable factors. In some embodiments, the shape of the epitaxialsource/drains 422 and 424 is a diamond-like shape.

In some embodiments, the semiconductor devices disclosed herein caninclude a first fin structure including a plurality of shallow recesssource/drain epitaxy structures 410 and a second fin structure includinga plurality of recessed fin structures 420.

In some embodiments, the semiconductor device can include a third finstructure. The third fin structure can include one or more diodes (e.g.,N+/p-type well diode or P+/n-type well diode), and/or one or morebipolar junction transistor (e.g., NPN bipolar junction transistor orPNP bipolar junction transistor).

FIG. 5 is a schematic view of an exemplary partially-fabricatedsemiconductor structure 500 including a plurality of semiconductordevices. The present disclosure provides a streamlined, simple, and costeffective process to fabricate n-type FinFET devices, p-type FinFETdevices, and other suitable semiconductor devices (e.g., bipolarjunction transistor structures and diodes) on the same substrate withoptimized drive current for the FinFET devices. As illustrated in FIG. 5, semiconductor structure 500 includes a partially-fabricated n-typeFinFET device 550 and a partially-fabricated p-type FinFET device 560formed on substrate 502. Semiconductor structure 500 can also includesuitable semiconductor structures, such as N+/p-type well diode 510, anexemplary P+/n-type well diode 520, an exemplary NPN: bipolar junctiontransistor 530, and an exemplary PNP bipolar junction transistor 540.The semiconductor structures formed on substrate 502 are furtherdescribed in FIGS. 6-8 .

In some embodiments, the semiconductor structures formed on substrate502 can be separated by STI structures 512. Substrate 502 can includevarious doped regions, such as p-type well 504 and n-type well 506 thatare respectively doped with p-type dopants and n-type dopants. Substrate502 can further include other suitable doped regions and are notillustrated in FIGS. 5-8 for simplicity. A dielectric layer, such asinterlayer dielectric layer (ILD) 580, is disposed on the semiconductorstructures and a plurality of interconnect structures 582 extendsthrough ILD 580 and are in contact with terminals of varioussemiconductor devices to provide electrical connections. Examples ofinterconnect structures can be through silicon vias (TSVs) formed ofconductive materials, such as cobalt, copper, tungsten, any suitableconductive material, and/or combinations thereof.

FIG. 6 is a schematic view of exemplary partially-fabricatedsemiconductor structures including a partially-fabricated n-type FinFETdevice 550, a partially-fabricated p-type FinFET device 560, andinterlayer dielectric (ILD) layer 580, in accordance with someembodiments. FILD layer 580 can include a dielectric material depositedusing a deposition method suitable for flowable dielectric materials(e.g., flowable silicon oxide, flowable silicon nitride, flowablesilicon oxynitride, flowable silicon carbide, or flowable siliconoxycarbide). For example, flowable silicon oxide can be deposited usingflowable CVD (FCVD). In some embodiments, the dielectric material issilicon oxide. In some embodiments, ILD layer 580 can have a verticalthickness along a z-axis in a range from about 50 nm to about 200 nm.Based on the disclosure herein, other materials, thicknesses, andformation methods for ILD layer 580 are within the scope thisdisclosure.

In some embodiments, partially-fabricated n-type FinFET device 550 caninclude substrate 502, dielectric layer 608, channel region 605, firstand second source/drain (S/D) regions 610, and STI regions 512. In someembodiments, dielectric layer 608 is a buried oxide layer of an SOIstructure and formed over p-type well 504. In some embodiments,substrate 502 is a p-type substrate. In some embodiments, substrate 502is Si (100). In some embodiments, first and second source/drain regions610 have n-type dopants.

In some embodiments, the partially-fabricated p-type FinFET device 560can include substrate 502, n-type well 506, buried channel region 615,first and second source/drain (S/D) regions 620, and STI regions 512. Insome embodiments, buried channel region 615 can be a portion of a finstructure. In some embodiments, buried channel region 615 andsource/drain (S/D) regions 620 can include SiGe. In some embodiments,substrate 502 can be a p-type substrate. In some embodiments, substrate502 is Si (100). In some embodiments, first and second source/drainregions 620 can have p-type dopants. In some embodiments, n-type well506 can be doped with n-type dopants to a nominal concentration. In someembodiments, n-type well can be formed in the substrate under the finstructures, by doping the substrate using ion implantation.

In some embodiments, n-type FinFET device 550 and p-type FinFET device560 can be respectively similar to n-type FinFET devices 250 andpartially-fabricated p-type FinFET devices 260 described above in FIG. 2. For example, fin structures of n-type FinFET device 550 can includesilicon having (110) or (100) rotated 45-degree ((100) R45) crystalorientation. In some embodiments, fin structures of p-type FinFET device560 can include SiGe having (100) crystal orientation. Similar toselection of crystal orientations for the FinFET devices described inFIG. 2 , selectively choosing a dual crystal orientation for the finstructures in FIGS. 5 and 6 , electron transport of n-type FinFET device550 and p-type FinFET device 560 can be optimized.

FIGS. 7A and 7B illustrate an exemplary N+/p-type well diode 510 (FIG.7A) and an exemplary P+/n-type well diode 520 (FIG. 7B) of semiconductordevice 500 in FIG. 5 , in accordance with some embodiments. TheN+/p-type well diode and P+/n-type well diode can include a third finstructure having SiGe. The p-type FinFET described above can alsoinclude SiGe in the fin structure. As such, the diode can be integratedwith the above disclosed FinFETs to form semiconductor devices. Inaddition, the diodes illustrated in FIGS. 8A-81B can include n-type andp-type regions formed using epitaxial growth processes similar to thosedescribed in FIG. 4M, such that different devices can be formed on thesame substrate without using additional fabrication steps.

Referring to FIG. 7A, an N+/p-type well diode 510 can be formed onsubstrate 502 and include a semiconductor structure 715, p-type region720, n-type region 710, a p-type well 504 formed in substrate 502 undersemiconductor structure 715, and an STI structure 512 between p-type andn-type regions 720 and 710 respectively. In some embodiments, n-typeregion 710 can include n-type dopants. In some embodiments, p-typeregion 720 and p-type well 504 can include p-type dopants. In someembodiments, semiconductor structure 715 can be a fin structure formedof SiGe.

Referring to FIG. 8B, a P+/n-type well diode 520 can be formed onsubstrate 502 and include semiconductor structure 715, p-type region740, n-type region 730, an n-type well 506 formed in substrate 502 undersemiconductor structure 715, and STI structure 512 between p-type andn-type regions 740 and 730 respectively. In some embodiments, n-typeregion 730 and n-type well 506 can include n-type dopants. In someembodiments, p-type region 740 can include p-type dopants.

In some embodiments, substrate 502 can be a bulk material, such as Si.In some embodiments, bulk SiGe, bulk germanium (Ge), SiGe on insulator,or Ge on insulator can be used as substrate 502. In some embodiments,semiconductor structure 715 can include SiGe. SiGe has severaladvantageous features. Since SiGe has a smaller band gap and therefore alower avalanche breakdown field than Si, it is particularly suitable forthe gated p-i-n diode employing the avalanche mechanism. With loweravalanche breakdown field, device reliability is improved since hotcarrier energy is lowered. Also, devices with SiGe in the doped regionscan induce compressive stress on the device channel and further enhancethe avalanche mechanism. SiGe can be epitaxially grown in a chamberhaving pressure of about 1 mTorr to about 100 Torr and grown to athickness of between about 2 nm and about 100 nm. The resulting Gecontent is between about 10% and about 80%. STI structure 512 can beformed by etching shallow trenches in substrate 502 and filling thetrenches with an insulator, such as silicon oxide.

FIGS. 8A and 8B illustrate an exemplary NPN bipolar junction transistor530 (FIG. 8A) and an exemplary PNP bipolar junction transistor 540 (FIG.8B) of semiconductor device 500 in FIG. 5 , in accordance with someembodiments. The bipolar junction transistor can include SiGe in the finstructure. The p-i-n diodes described above can include SiGe in thechannel. And the p-type FinFET described above can also include SiGe inthe fin structure. As such, the bipolar junction transistor can beintegrated with the above disclosed FinFETs and p-i-n diodes to formsemiconductor devices.

Referring to FIG. 8A, an NPN bipolar junction transistor 530 can includea substrate 502, a semiconductor structure 715, a first doped region810, a second doped region 820, a third doped region 830, a p-type well504 formed within substrate 502 under semiconductor structure 715, ann-type well 506, and an STI structure 512. In some embodiments, firstdoped region 810 can include an collector region. In some embodiments,second doped region 820 can include a base region. In some embodiments,third doped region 830 can include an emitter region. In someembodiments, first doped region 810 and third doped region 830 caninclude a first type dopant and second doped region 820 can include asecond type dopant opposite to the first type (e.g., thecollector/emitter region can have a different type of dopant than thatof the base region). In some embodiments, first doped region 810 andthird doped region 830 can include n-type dopants as the first typedopant. In some embodiments, second doped region 820 can include p-typedopants as the second type dopant. In some embodiments, semiconductorstructure 715 can be a fin structure including SiGe.

Referring to FIG. 8B, a PNP bipolar junction transistor 540 can includesubstrate 502, semiconductor structure 715 with a first doped region840, a second doped region 870, a third doped region 880, an n-type well506 formed within substrate 502, and STI structure 512 formed betweendoped regions. In some embodiments, first doped region 840 can includean emitter region. In some embodiments, second doped region 870 caninclude a base region. In some embodiments, third doped region 880 caninclude a collector region. In some embodiments, first doped region 840and third doped region 880 can include a first type dopant and seconddoped region 870 can include a second type dopant opposite to the firsttype. In some embodiments, first doped region 840 and third doped region880 can include n-type dopants. In some embodiments, first doped region840 and third doped region 880 can include p-type dopants. In someembodiments, second doped region 870 can include n-type dopants. In someembodiments, semiconductor structure 715 extends laterally throughsubstrate 502. In some embodiments, semiconductor structure 715 can be afin structure including SiGe.

Various embodiments in accordance with this disclosure provide asemiconductor device. The semiconductor device can include a substrate,a first fin structure including a first material having a first topsurface crystal orientation, and a second fin structure including asecond material having a second top surface crystal orientation. Thesecond material can be different from the first material. And the secondcrystal orientation can be different from the first top surface crystalorientation.

Various embodiments in accordance with this disclosure also provide asemiconductor device. The semiconductor device can include a substrate,a first fin field effect transistor (FinFET), a second FinFET, and athird fin structure, disposed on the substrate. The first FinFET caninclude a first fin structure with a first material having a first topsurface crystal orientation. The second FinFET can include a second finstructure with a second material having a second top surface crystalorientation. The second material can be different from the firstmaterial. And the second top surface crystal orientation can bedifferent from the first top surface crystal orientation. The third finstructure can include SiGe.

Various embodiments in accordance with this disclosure also provide amethod of fabricating a semiconductor device. The method can includeproviding a substrate with a device layer; removing a portion of thedevice layer; forming a SiGe epitaxy layer over a portion of thesubstrate, where the device layer on the portion of the substrate isremoved; and etching the device layer and SiGe epitaxy layer to form afirst fin structure including a first material having a first topsurface crystal orientation and a second fin structure including asecond material having a second top surface crystal orientation. Thesecond material can be different from the first material. And the secondcrystal orientation can be different from the first top surface crystalorientation.

It is to be appreciated that the Detailed Description section, and notthe Abstract of the Disclosure, is intended to be used to interpret theclaims. The Abstract of the Disclosure section can set forth one or morebut not all exemplary embodiments contemplated and thus, are notintended to be limiting to the subjoined claims.

The foregoing disclosure outlines features of several embodiments sothat those skilled in the art can better understand the aspects of thepresent disclosure. Those skilled in the art will appreciate that theycan readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodimentsintroduced herein. Those skilled in the art will also realize that suchequivalent constructions do not depart from the spirit and scope of thepresent disclosure, and that they can make various changes,substitutions, and alterations herein without departing from the spiritand scope of the subjoined claims.

What is claimed is:
 1. A method for forming a semiconductor structure,comprising: providing a silicon-on-insulator (SOT) substrate comprisinga device layer, a buried oxide (BOX) layer, and a silicon substrate,wherein a first crystal orientation of the device layer is differentfrom a second crystal orientation of the silicon substrate; removing aportion of the device layer to expose a portion of the siliconsubstrate; forming a silicon germanium (SiGe) epitaxy layer on the SOIsubstrate; forming a first fin structure in the device layer; andforming a second fin structure in the SiGe epitaxy layer.
 2. The methodof claim 1, wherein forming the SiGe epitaxy layer comprises depositinga SiGe material on the exposed portion of the silicon substrate.
 3. Themethod of claim 1, wherein forming the SiGe epitaxy layer comprisesforming a spacer on top and side surfaces of the device layer to isolatethe SiGe epitaxy layer and the device layer.
 4. The method of claim 1,further comprising planarizing top surfaces of the device layer and theSiGe epitaxy layer.
 5. The method of claim 1, wherein forming the firstfin structure comprises removing another portion of the device layer, aportion of the BOX layer, and another portion of the silicon substrate.6. The method of claim 1, wherein forming the second fin structurecomprises removing a portion of the SiGe layer and another portion ofthe silicon substrate.
 7. The method of claim 1, further comprisingforming a shallow trench isolation (STI) recess between the first andsecond fin structures.
 8. A method for forming a semiconductorstructure, comprising: removing a portion of a device layer of asilicon-on-insulator (SOI) substrate and a portion of a buried oxide(BOX) layer of the SOI substrate to expose a silicon substrate of theSOI substrate, wherein the portion of the device layer and the portionof the BOX layer are in a first region of the SOI substrate; forming asilicon germanium (SiGe) epitaxy layer in the first region of the SOIsubstrate; forming a first fin structure in the first region of the SOIsubstrate and having a first crystal orientation perpendicular to theSOI substrate; and forming a second fin structure in a second region ofthe SOI substrate and having second crystal orientation perpendicular tothe SOI substrate.
 9. The method of claim 8, wherein forming the SiGeepitaxy layer comprises depositing a SiGe material on an exposed portionof the silicon substrate.
 10. The method of claim 8, wherein: the firstcrystal orientation is (100); and the second crystal orientation is(110).
 11. The method of claim 8, further comprising planarizing topsurfaces of the device layer and the SiGe epitaxy layer.
 12. The methodof claim 8, wherein forming the second fin structure comprises removinganother portion of the device layer, another portion of the BOX layer,and portion of the silicon substrate.
 13. The method of claim 8, whereinforming the first fin structure comprises removing a portion of the SiGelayer and a portion of the silicon substrate.
 14. The method of claim 8,further comprising forming a gate structure over the first and secondfin structures.
 15. A method for forming a semiconductor structure,comprising: forming a device layer and a dielectric layer on a firstregion of a substrate; forming a silicon germanium (SiGe) epitaxy layeron a second region of the substrate and having a second crystalorientation different from a first crystal orientation of the devicelayer; forming a first fin structure in the first region of thesubstrate; forming a second fin structure in the second region of thesubstrate; and reducing a height of the first and second fin structures.16. The method of claim 15, wherein forming the SiGe epitaxy layercomprises forming a spacer on top and side surfaces of the device layerto isolate the SiGe epitaxy layer and the device layer.
 17. The methodof claim 15, further comprising planarizing top surfaces of the devicelayer and the SiGe epitaxy layer.
 18. The method of claim 15, whereinforming the SiGe epitaxy layer comprises etching the SiGe material toform a slanted sidewall.
 19. The method of claim 15, further comprisingforming source/drain structures on the first and second fin structures.20. The method of claim 15, wherein the first crystal orientation isrotated 45-degrees with respect to the second crystal orientation.